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參數(shù)資料
| 型號(hào)： | Si9961 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | 12-V Voice Coil Motor Driver(用于光盤(pán)驅(qū)動(dòng)頭定位系統(tǒng)的12V語(yǔ)音線(xiàn)圈電機(jī)驅(qū)動(dòng)器) |
| 中文描述： | 12 V的音圈電機(jī)驅(qū)動(dòng)器（用于光盤(pán)驅(qū)動(dòng)頭定位系統(tǒng)的12V的語(yǔ)音線(xiàn)圈電機(jī)驅(qū)動(dòng)器） |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大?。?/td> | 258K |
| 代理商： | SI9961 |
Si9961
Vishay Siliconix
S-60752—Rev. F, 05-Apr-99
6
FaxBack 408-970-5600, request 70014
www.siliconix.com
User-Programmable Gains
During linear operation, the transconductance amplifiers’
gains (input voltage at V
IN
vs. VCM current, in Figure 1) are
set by external resistors R
3
R
5
, R
SA
, and R
SB
and selected
by gain input. After selecting a value for R
SA
and R
SB
that will
yield the desired VCM current level, the High and Low
feedback gain ratios may be determined by the following:
R
5
R
3
S
R
5
R
4
S
Where
R
S
= R
SA
= R
SB
Input offset current may then be calculated as:
R
---------------------------
Where
R
IN
= R
3
or R
4
Head Retract
A low on the RETRACT input pin turns output devices Q1 and
Q4 on, and output devices Q2 and Q3 off. Maximum VCM
current can be set during head retract by adding an external
resistor between the IRET pin and ground. Maximum retract
current may be calculated as:
Head retract can be initiated automatically by an undervoltage
condition (either the 12-V or 5-V supplies on the Si9961) by
connecting the FAULT output to the RETRACT input.
A high ENABLE input puts both driver outputs in a high-
impedance state. The ENABLE function can be used to
eliminate quiescent output current when power is applied but
the head has been parked, such as a sleep mode. A sleep-
mode power down sequence should be preceded by a retract
signal since a power failure during this state may not provide
Transconductance Amplifier Compensation
The Si9961CY features an integrated transconductance
amplifier to drive the voice coil motor (VCM). To ensure proper
operation, this amplifier must be compensated specifically for
the VCM being driven. As a first approximation, the torque
constant and inertia of the VCM may be ignored, although
they will have some influence on the final results, especially if
large values are involved (Figure 1).
Frequency Compensation
The VCM transconductance (in siemens) of this simplified
case may be expressed in the s (Laplace) plane as:
1
L
v
v
Where
R
v
= VCM resistance in ohms
L
V
= VCM inductance in henrys
s is the Laplace operator
In this case, the transconductance pole is at -Rv/Lv. It is
desirable to cancel this pole in the interest of stability. To do
this, a compensation amplifier is cascaded with the VCM and
its driver. The transfer function of this amplifier is:
L
Where
R
L
= Compensation amplifier feedback resistor in ohms
C
L
= Compensation amplifier feedback capacitor in farads
A = Compensation amplifier and driver voltage gain at high frequency
If R
L
x C
L
is set equal to L
v
/R
v
, then the combined open loop
transconductance in siemens becomes:
v
+
In this case, the transconductance has a single pole at the
origin. If this open loop transfer is closed with a
transimpedance amplifier having a gain of B ohms, the
resultant closed loop transconducatance stage has the
transfer function (in siemens) of:
A
L
B
×
L
v
Where
B = Current feedback transimpedence amplifier gain in ohms.
The entire transconductance now contains only a single pole
at -A B/Lv. A and B are chosen to be considerably higher
than the servo bandwidth, to avoid undue phase margin
reduction.
As a typical example, in the referenced schematic, assume
that Rsa and Rsb = 0.5
, R
5
= R
3
= 10 k
, VCM inductance
(Lv) = 1.5 mH, VCM resistance (Rv) = 15
. Hence:
R
v
= 15
L
v
= 1.5 mH
B = 2
A = 16 x R
L
/10000
C
L
= L
v
/(R
v
x R
L
) = 100 x 10
-6
/R
L
farads
Gain Optimization
There are three things to consider when optimizing the gain
(A) above. The first is servo bandwidth. The main criterion
here is to avoid having the transconductance amplifier cause
an undue loss of phase margin in the overall servo
(mechanical + electrical + firmware) loop. The second is to
avoid confirguing a bandwidth that is more than required in
view of noise and stability considerations. The third is to keep
the voltage output waveform overshoot to a level that will not
cause cross-conduction of the output FETs.
High Gain
------
------------
=
GAIN SELECT Input=High
(
)
Low Gain
------
------------
=
GAIN SELECT Input=Low
(
)
I
OS
S
------------
=
R
+
)
IN
V
OSA2
5 V
IAS3
+
I
OUT
175
I
ret
×
175
ret
---------------
×
=
=
g
v
-----
s
R
v
------
+
÷
=
H
c
A
s
-------------------
+
----------------------------------
×
=
g
tc
--------------
=
g
to
-----
s
-------------
+
-----------------------
=
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SI9961A | 制造商:VISHAY 制造商全稱(chēng):Vishay Siliconix 功能描述:12-V Voice Coil Motor Driver |
| SI9961ACY | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Voice Coil Driver RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類(lèi)型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| SI9961ACY-E3 | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Voice Coil Driver RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類(lèi)型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| SI9961ACY-T1 | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Voice Coil Driver RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類(lèi)型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| SI9961ACY-T1-E3 | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Voice Coil Driver RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類(lèi)型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
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